Magnetic and Structural Properties of Ferromagnetic GeMnTe Layers

Abstract

Ferromagnetic Ge_1−xMn_xTe thin films with x≤0.19 were deposited on (111) oriented BaF₂ monocrystals using molecular beam epitaxy technique. X-ray diffraction carried out at high temperatures for samples with x≤0.05 revealed ferroelectric transition from rock-salt to rhombohedral structure at T=625–675 K. The magnetic properties investigated with SQUID magnetometry and ferromagnetic resonance technique exhibit an easy magnetization direction normal to the plane in as grown samples. We attribute this finding to lattice strain due to mismatch of thermal expansion coefficients or to the crystalline stress related to inhomogeneous distribution of Mn ions in the sample volume. Thermal treatment changes the easy axis into in-plane direction which can be associated with distinct improvement of the structural properties.